The present invention pertains to devices and systems used in hospitals to monitor vital signs associated with a hospitalized patient. More particularly, the device of the present invention is directed to portable patient vital sign monitors which can receive and process raw vital sign data from a variety of vital sign transducers associated with an ambulatory patient and transmit the processed vital sign data to a remote location.
Health care professionals are fully aware of the need to monitor, on a frequent or continuous basis, the vital signs associated with a hospitalized patient, particularly those who are seriously ill. Virtually every hospitalized patient requires periodic measurement and logging of temperature, pulse rate, and blood pressure. Many patients also need frequent determination of respiration rate, cardiac activity, and pulse oximetry. Such monitoring has typically been performed by having a health care worker periodically visit the bedside of the patient and measuring and/or observing the patient's vital signs using dedicated equipment that is either hooked up to the patient or brought into the patient's room. Such a monitoring procedure is not ideally cost effective because if all hospitalized patients are monitored in this way, it is highly labor intensive. Further, the monitoring of patients who may be ambulatory, or who may wish to be ambulatory, cannot effectively be accomplished by either continual bedside monitoring or by frequent visitation by a health care worker.
In an attempt to improve the efficiency of vital sign monitoring under these conditions, a number of devices and systems have been developed which have been only partially effective. For example, in U.S. Pat. No. 3,638,642, a monitoring system is described in which the patient wears a sensor unit capable of monitoring temperature, pulse, and a single channel ECG. The monitored information is transmitted back to the patient's room where it can be observed on a bedside monitor. However, the system of the '642 patent is deficient in that it cannot handle other patient vital signs such as non-invasive blood pressure, respiration, pulse oximetry, and multiple channel ECG. Further, it does not provide for transmission of the patient vital signs to a centralized monitoring system.
The remote ECG monitoring system of U.S. Pat. No. 3,986,498 provides a patient worn ECG sensor and transmitter device which sends signals to a receiving unit located in the patient's room, which can re-transmit the monitored signals to a central monitoring station. The system of the '498 patent, however, does not allow for simultaneous display and monitoring of other patient vital signs.
A physiological data monitoring system is described in U.S. Pat. No. 4,784,162, which includes sensors for breath sounds, respiration, left and right ECG, position indication, and patient activity. It does not allow for convenient remote monitoring of all necessary patient vital signs.
A belt worn by a patient is shown in U.S. Pat. No. 4,909,260 to provide the ability to remotely monitor and transmit ECG signals as well as respiration data. A clip-on display is further provided. However, this device is limited in its ability to monitor, display, and transmit all needed vital signs.
A fully integrated hospital network for coordinating a variety of bedside patient monitoring devices is disclosed in U.S. Pat. No. 5,319,363. The system of the '363 patent also integrates certain RF medical telemetry devices used on ambulatory patients. However, it does not show the use of a portable device which is convenient to carry, self-contained, and capable of displaying and transmitting a plurality of vital sign parameters.
The advent of miniaturization in the field of mechanics and electronics has made possible today what was unattainable as recently as five years ago. Ideas deemed revolutionary at that time are now producing an entirely new line of compact, robust, low power devices for use by the medical profession.
A person's vital signs, namely heart rate, blood pressure, blood oxygen content, body temperature and respiration, when reported in real time, are the main body parameters thought to be indicative of that person's state of wellness at any given time. The ability to provide a safe and unobtrusive method of acquiring these parameters in real time while allowing patient mobility, has been a long sought effort in the medical instrumentation profession. To date, efforts to produce such a device have been limited to those defined as stationary or battery operated, but not worn by the patient due to excessive size and/or power requirements.
What was not known by the industry was a method whereby all the above mentioned knowledge could be assembled in a manner to produce a device meeting the requirements for a real time vital signs monitor as heretofore described. For example, the use of surface mount components in conjunction with low voltage circuit design results in a vastly superior RF circuit design as opposed to the use of each technology by itself Also lacking in the prior art was a means of utilizing a single low voltage precision valve to operate as both a controlled variable bleed and a dump valve in order to facilitate the demanding blood pressure requirements necessary for accuracy when using the oscillometric noninvasive method for blood pressure.
The means to successfully design a low voltage respiration circuit which does not incorporate the impedance pneumography, thus minimizing the effects of artifact interference due to abrupt changes in chest wall resistance and the presence of unwanted electrical signals is not general knowledge. The method of incorporating a processor based algorithm to enhance a low voltage temperature circuit design as a means of obtaining high resolution temperature data is not widely known nor in general use.
None of the prior art remote patient monitoring devices combine the ability to simultaneously display and transmit to a remote location respiration, non-invasive blood pressure, temperature, dual channel ECG, and pulse oximetry. Further, no prior art devices allow for remote transmission of a plurality of patient vital signs along with the ability to use the patient monitoring device as a portable stand-alone unit. Further, prior art devices which provide for monitoring at remote locations of a plurality of patient vital signs do not also include the ability of the health care worker to start and stop recording units at the central monitoring station by transmitting a record command signal from the remote patient monitoring device. Such a device is needed.